Finished leather split



May 14, 1963 SHU-TUNG TU FINISHED LEATHER SPLIT Filed May 2, 1960 Inventor 5hu-Tung Tu By his fifzorney United States Patent Ofifice 3,089,781 Patented May 14, 1963 3,089,781 FINISHED LEATHER SPLIT Shu=Tung Tu, Ipswich, Mass, assignor to United Shoe Machinery Corporation, Boston, Mass., a. corporation of New Jersey Filed May 2, 196% Ser. No. 26,205 3 Claims. (Cl. 117-11) This invention relates to an improvement in the surface character of finished flesh side leather splits.

Leather is regularly passed through a splitter which cuts off a layer from the flesh side, i.e., the flesh side split, to bring the remainder or grain side to uniform desired thickness for fabrication. The flesh side split has an uneven texture, with fine free fibers at the cut surface. The nature of this surface interferes with providing a clear finish and heretofore, heavy, usually opaque and artificial-appearing finishes or special embossing, have been used to cover up the surface. Splits so finished are unsuitable for many purposes and the finished splits do not command a good price.

It is an object of the present invention to provide an improved surface character for flesh side leather splits to closely resemble grain leather.

To this end and in accordance with a feature of the present invention, the natural arrangement of the fibers of the splits both at the surface and internally is altered so that the fiber arrangement corresponds to a considerable extent to fiber arrangement in grain leather. The altered fiber arrangement is held in fixed position by a resin polymer and with further treatment with conventional leather finishes. The resulting leather material approaches grain leather in appearance and other properties.

I have found that flesh side splits penetrated with needle points at closely spaced points over substantially the entire surface area forming very small crater holes have the arrangement of the fibers altered. The rearrangement of the fibers is locked in by a limited deposit of a fluid hardenable polymer composition on the surface and sides of the small holes. The holes of the split are thus prevented from swelling and closing and the fibers reverting to their original arrangement if aqueous or non-aqueous compositions are used in subsequent finishing operations.

It appears that this fiber rearrangement includes pulling the surface fibers between holes into a more taut alinement by the process of forcing the needle points into the leather, and also that the loose end surface fibers are pushed down against the sides of the holes. This fiber rearrangement provides a firmer, smoother surface to which finishing compositions adhere more firmly. Additional advantages are that the holes, which actually resemble hair follicle holes in grain leather, give improved softness and porosity and improve the absorption of liquid finishes.

The invention will be described further in connection with the drawing forming part of the disclosure, in which FIG. 1 is a diagrammatic cross section on an enlarged scale of a section of a flesh-side split before treatment;

FIG. 2 is a diagrammatic cross section on an enlarged scale illustrating a flesh-side split after forming holes therein according to the present invention;

FIG. 3 is a diagrammatic cross-section on an enlarged scale taken on line IIIIII of FIG. 2 illustrating the fiber arrangement of a flesh-side split after forming holes therein according to the present invention; and

FIG. 4 is a diagrammatic cross section on an enlarged scale illustrating a flesh-side split after forming holes therein according to the present invention, and illustrating the action of a plastic coating deposited on the surface.

Holes are impressed in a flesh-side split, previously tanned by a desired method, in closely spaced relationship over its entire area. The holes are impressed by needling the surface area by smooth-surfaced pointed needles, either manually or by devices especially suited for that purpose. A suitable device is that disclosed in the application of Shu-Tung Tu and John H. Highberger, Serial No. 805,032, filed April 8, 1959, entitled Collagen Fiber Sheet Material and Method of Making, and 0perated in a similar manner in the present invention. The device comprises a reciprocating needle bar carrying one or more rows of needles and movable to carry the needles into and out of hole-forming engagement with a split which is supported on an adjustable bed member. The needles are clamped in place, their points projecting evenly between the needle bar and a clamping plate. The needles are simple pointed needles comparable to the traditional steel phonograph needles, and are spaced closely, from about /8 to about /2" apart, in order to make a large number of holes with each stroke.

The simple, smooth-surfaced pointed needles, preferably closely spaced, penetrate the firm surface 10 of the split 12 through the closely packed fibers 14, as shown in FIG. 1, pushing down the upstanding surface fibers 16 into the formed holes 18, and also pushing down the fibers 14 encircling the holes 18 to pack these fibers against the sides to form a relatively smooth-surfaced, crater-shaped hole, as shown in FIG. 2. The surface fibers 14 between any two holes appear to be pulled taut across the surface 10, i.e., more or less aligned, rounding off the top contour 20 of each hole, thus rendering the top surface relatively smooth and even.

The needling process does not merely indent the exterior surface of the split to leave an embossed impression, but actually displaces the fibers to make a welldefined hole. In fact, it will be observed that the net effect of the needle penetration of the flesh-side split is closely parallel to the natural interruption of fibers caused by sweat glands, pores and hair follicles normally extending into a grain split skin. By adjustment of the height of the needles above the skin surface the points may either penetrate partially the thickness of the split, approximating a true hair follicle cavity, or penetrate completely, where increased porosity is sought. A random distribution of the holes is preferred rather than regular alignment, and is best achieved by passing the split back and forth beneath the needles at a relatively fast pace rather than to move it slowly in a single direction. Desirable products have been obtained where there are as few as 600 or as many as 6000 holes per square inch in the split. The diameter of the holes at the surface is governed by the diameter of the needles used, and the depth of their penetration. Preferably the punctured holes are between 0.1 mm. and 0.2 mm. in diameter at the skin surface.

The surface 10 of the split 12 after the needling process shows, as in FIG. 3, a multitude of very small cratershaped holes 18 breaking the extended surface area 10 for a continued interruption of the fiber structure. No loose fibers 16 are apparent on the surface 10, since they have been impressed into the holes 18 by the needle pressure. The bundles of fibers 14 at the surface 1%) are pushed into tightly packed swirls 22 surrounding each indenture l8, and being pulled down inward from the perimeter of the hole 18, tautly pull the surface fibers 14 extending between any two or more hole punctures 18.

It has been found that to prevent closure of the holes when the split is subjected to further treatment with liquids, it is desirable to deposit a plastic material 24 on the sides of the holes 1-8 of the split 12, as shown in PEG. 4. The film of plastic permits the holes to retain their contour, i.e., the fibers pressed against the hole sides by the puncturing needle do not relax when wet to close the hole. The plastic deposit may be provided by spreading, as by brushing or spraying, a fluid hardenable polymer material on the surface of the split into which the needles have penetrated. The fluid material is preferably wiped with a sponge, knife or squeegee to remove undesired excess of material from the exposed portions of the split and to force the fluid polymer material into the holes 18. The polymer material is then allowed to harden.

Suitable fiuid polymer compositions include aqueous emulsions or latices of polymer resinous materials and volatile organic solvent solutions of polymeric materials. Aqueous emulsions which have been found useful include emulsions of the polymers and copolyrners of ethyl and methyl esters of acrylic and/ or rnethacrylic acids, emulsions of polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal and latices of various natural and synthetic rubbers and combinations of the above. It has been found that the natural and synthetic rubber latices may be blended with emulsions or latices of resinous polymers with which they are compatible and will serve as solid plasticizers. An aqueous emulsion or latex or a volatile organic solvent solution of polysulfide (Thiokol LP) is particularly desirable in this regard in that it facilitates penetration and also serves as a wash-resistant plasticizer to give desired softness and stretch. In the emulsions it has been found that 5% solids emulsions are most suitable but higher solids content emulsions may be used. Any desired Weight of coating material may be used, but about 10% coating material based on the weight of the split has been found to give a very desirable product.

Volatile organic solvent solutions useful in treatment of the needled split material include solutions of such resins as polyesters, alkyds, epoxide resins, polysuifite resins, nitrocellulose, cellulose acetate, polyurethanes and polyamides. Useful coating compositions may contain from 10% to 50% by weight solids.

Additional finishing treatments may be applied over this initial base film of plastic. Also, the treated split with or without subsequent treatment with fluid resin may be finished, as by smooth plating. The vivid duplication of natural grain is Well demonstrated without embossing.

The following example is given as of possible assistance in understanding the invention, but it is to be understood that the invention is not limited to the specific materials or conditions shown in the example:

Example A flesh-side, chrome-tanned steer leather split was passed beneath a reciprocating bar carrying needles on its lower surface, and was manipulated beneath the needle bar to provide an average of about 1500 perforations in the surface per square inch. The diameter of the holes was found to be from about 0.1 to about 0.2 mm. when examined under a microscope. The holes penetrated about three-quarters through the thickness of the split.

After needling treatment a 20% solids solution of a butadiene-acrylonitrile copolymer latex was spread on the surface of the split. The latex containing 10% (on the solid basis) of a wetting agent and 5% resin solids on the weight of the split was spread on. The wetting agent insured rapid wettin and penetration of the needling holes of the split. The split was dried and thereafter a conventional acrylic resin emulsion finish, i.e., a Primal finish, was spread on the surface and allowed to dry.

Thereafter, the split was finished by conventional procedures, including application of a commercial base coat containing pigment, wax and resin. The split was smooth plated by the usual commercial plating procedure and finally a coat of an aqueous dispersion of lacquer was applied as a topcoat and the split was plated.

The finish flesh-side split had a tight smooth surface finish and a pliable feel with an appearance similar to a grain pattern on the surface.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. As an article of manufacture, a tanned flesh side leather split material having a surface characteristic of grain leather, said surface being formed with a multiplicity of very small crater-shaped holes over its entire surface, said holes. being from about 600 to about 6000 holes per square inch and from about 0.1 mm. to about 0.2 mm. in diameter, and resin deposited on sides of said holes to reinforce said holes against swelling and closing.

2. As an article of manufacture, a tanned flash side leather split material having a surface characteristic of grain leather, said surface being formed with a multiplicity of very small crater-shaped holes over its entire surface extending partially through the thickness of said split, there being from about 600 to about 6000 holes per square inch and the holes being from about 0.1 mm. to about 0.2 mm. in diameter, and resin deposited on sides of said holes to reinforce said holes against swelling and closing.

3. As an article of manufacture, a tanned flesh side leather split material having a surface characteristic of grain leather, said surface being formed with a multiplicity of very small crater-shaped holes over its entire surface extending completely through the thickness of said split, there being from about 600 to about 6000 holes per square inch and the holes being from about 0.1 mm. to about 0.2 mm. in diameter, and resin deposited on sides of said holes to reinforce said holes against swelling and closing.

References Qited in the file of this patent UNITED STATES PATENTS 2,021,163 Woodman Nov. 19, 1935 FOREIGN PATENTS 389,662 France July 6, 1908 

1. AS AN ARTICLE OF MANUFACTURE, A TANNED FLESH SIDE LEATHER SPLIT MATERIAL HAVING A SURFACE CHARACTERISTIC OF GRAIN LEATHER, SAID SURFACE BEING FORMED WITH A MULTIPLICITY OF VERY SMALL CRATER-SHAPED HOLES OVER ITS ENTIRE SURFACE, SAID HOLES BEING FROM ABOUT 600 TO ABOUT 6000 HOLES PER SQUARE INCH AND FROM ABOUT 0.1 MM. TO ABOUT 0.2 MM. IN DIAMETER, AND RESIN DEPOSITED ON SIDES OF SAID HOLES TO REINFORCE SAID HOLES AGAINST SWELLING AND CLOSING. 